Equilibrium, Statistical

that state of a closed statistical system in which the average values of all the physical quantities characterizing the state are independent of time. Statistical equilibrium is one of the basic concepts of statistical mechanics, where it plays the same role as thermodynamic equilibrium in thermodynamics. Statistical equilibrium is not balanced in the mechanical sense, since small fluctuations do not cease in the system when this state obtains. The theory of statistical equilibrium is given in statistical mechanics, which describes statistical equilibrium in terms of Gibbs’ microcanonical, canonical, or grand canonical ensembles, depending on the type of contact between the system and its surroundings.